The ability of a disposable absorbent article to sense wetness, soiling, or a change of condition has been routinely recognized by manufacturers, as a desirable feature for a variety of modern hygiene products. Disposable absorbent articles such as infant (baby care) and child care diapers, and training pants; adult incontinence pads, pants and briefs; feminine sanitary products such as pads, napkins, tampons, and liners; wiping products; bed liners and the like, are highly absorbent and efficiently pull moisture away from a surrounding environment. However, given these products' ability to absorb large quantities of aqueous liquid, they may easily become saturated, much to the surprise of a product user or caregiver.
In the case of disposable personal care absorbent articles which are to be worn next to a user's body, reducing skin irritation caused by prolonged wetness exposure is of utmost concern. Because these articles are so absorbent, wearers or caregivers may also not realize the products have been soiled, particularly if the topsheet facing the user, and of which a caregiver touches during use, may appear dry. If users are inexperienced toddlers or incapacitated individuals who may not recognize the meaning of body sensations associated with urination or soiling, they may also not be able to appreciate that a product needs to be changed. In any event, the saturation of such absorbent products may also eventually lead to product leakage and subsequently, to embarrassing garment odors and unsightly stains.
In the case of discreet absorbent articles that cannot be easily viewed by a consumer during product usage, except by undressing (such as sanitary napkins), consumers may further not appreciate the actual saturation level of a product, ahead of an imminent leakage event. Thus, the caregiver or wearer may not recognize that the article is ready to be replaced or that leakage may shortly occur. Leakage from such discreet products may result in undergarment, outergarment or bedding stains.
Visual indicator mechanisms have therefore been employed by consumer absorbent product manufacturers for some time, to signal the presence of wetness or a change in condition of the absorbent articles. See for example, JP2000-279442, which describes a color changing ink. A large number of wetness sensing and visual indicator technologies currently exist, including electronic-based wetness sensors, ink-based color changing wetness indicators, enzyme or other chemical-based sensors which change appearance upon a change in chemistry within a product, pH change-based indicators, and temperature change-based wetness indicators. Such wetness indicators each typically provide visual or audible indication of article soiling by a color changing, a color disappearing or a color appearing, or by the emission of a sound. Such wetness indicators may simply consist of water soluble inks which disappear upon contact with liquid moisture.
Much of the heretofore described wetness sensing and signalling technology is frequently impractical for implementation in absorbent articles, as the technology is too expensive to implement on relatively lower-cost products. Further, certain chemistries, such as enzyme-based wetness sensors, may have stability issues. Water-soluble, dye-based wetness indicators also often lack the high detection sensitivity desirable for use in new-born diapers. They also may provide poor color contrast which sometimes makes signal reading difficult. There is therefore a need for a practical, sensitive wetness indicator technology that can be easily implemented in a wide array of absorbent articles.
While certain color changing ink-based sensing technology has advanced, and is affordable for large scale absorbent article implementation, such technology may not be as effective for certain absorbent article applications in which the physical location of a user and placement of the article prevents the easy checking of a visual sensor. For example, while color changing ink-based wetness indicators may easily be used for situations in which a user is confined to a bed or other location looked after by a caregiver, or where the article is readily visible, such as on the exposed diaper of a sleeping or crawling infant or walking toddler, such technology offers less advantages for feminine care absorbent articles, or for adult care absorbent articles to be used by active adults, which are not readily visible and for which discretion is of the utmost user concern.
Olfactory or fragrance-based wetness indicators have also been described to provide an alternative to visual indication of article soiling. For example, olfactory wetness signals are described in US2009/0221980 to Mosbacher et al. Such reference describes the use of malodorous materials in an absorbent article, as well as the use of volatile esters to provide a pleasant aromatic scent upon the degrading of encapsulation materials or a storage pouch by liquid moisture, the encapsulation or pouch materials being used to contain the volatile fragrance within the absorbent article.
Fragrances are also frequently described for general use in absorbent articles to mask the body odors of sweat, urine, menses or bowel movements. However, fragrance indicators and masking components are often unstable due to their inherent volatility, such as being derived from essential oils. Such chemistry often demonstrates short shelf lives and as a result, presents packaging, manufacturing, and extended use concerns. There is therefore a need for olfactory wetness indicators that do not solely rely on encapsulation or storage containers (at added cost). There is a further need for such indicators that have prolonged shelf-lives.
In an attempt to provide a controlled odor masking effect over urine in disposable sanitary products, US2008/0139378 to Hildebrand et al., describes the use of non-volatile organopolysiloxane formulations to deliver odor control functionality. Upon contact with urine, a fragrance alcohol is released by acid-catalyzed hydrolysis of betaine functional groups carrying a radical of a fragrance alcohol on the organopolysiloxane molecule. As noted in the reference, the release of a fragrance alcohol occurs selectively upon contact with acidic urine. Such functional groups are described as being more stable against hydrolysis at a neutral pH. Therefore, use of such high molecular weight chemistry in neutral or non-acidic environments is not described as delivering fragrance functionality, and no other indicator technology is described as useful with such chemistry. Furthermore organopolysiloxane chemistry is often used to impart hydrophobic attributes to products. As such, it poses use challenges within absorbent articles, in that the hydrophobic chemistry significantly impacts aqueous-based liquid flow and absorption pathways. Such organopolysiloxane chemistry includes large polymer molecules, which are often costly and may be difficult to place in solution. A need therefore exists for a controlled odor masking system that is readily released upon occurrence of a soiling event (not the result of a relatively slow hydrolysis reaction), which does not significantly hinder absorbency pathways, and which is readily soluble.
To combine numerous sensing technologies or wetness indicator technologies with other chemical functionality is cost prohibitive, and presents practical challenges in disposable absorbent article manufacture. Furthermore, the separate implementation of odor masking/signaling chemistry and visual wetness indicating/coating technology adds additional manufacturing steps as well. A need therefore exists, for signaling technology for disposable absorbent articles which can provide multisensory wetness and absorbent capacity signals to consumers, and which also masks body exudate odors.
Thus, a need exists for a coating chemistry technology that is of relatively low cost, and easy to be implemented in the manufacture of absorbent products, and which may be capable of being combined with other chemical functionality to achieve enhanced benefits, such as capacity indicators. A need also exists for a relatively stable wetness indicator composition which offers multiple signals in a single composition to a caregiver or consumer, that is not limited in its triggerability by pH chemistry of wetness, and which is not hindered by the normally short shelf life common to volatile fragrances and essential oils. Finally, a need also exists for indicator composition systems which offer relatively less interference with absorbency channels in an absorbent article.